Age to integrate pullets

OK, so I'm planning to add 2 new hens to my tiny flock (was 3, now down to 2 after Olivia's untimely and sad passing ). I was at the home of my client who raises chickens the other day, and I choose 2 pullets. They are 5-6 weeks old now. Obviously if one or both turn out to be roosters I'll have to re-choose, but she thinks these are hens.

I can't take them for a month and then they will be in quarantine for another month, so by the time we're done w/ that they will be 3.5-4 months old. Is that a safe age at which to put them in w/ my 2 adult hens?

They're VERY cute. Bianca is a mostly white Brahma X and Audrey is all black. I didn't have my camera, alas, but I'll try to get my client to take some pics. We put zip ties on their legs to distinguish them. They are more friendly than some of the others b/c that clutch was fostered out for a few weeks to a friend of hers w/ children so they were loved on and handled. You could tell the difference just picking them up. Audrey actually sat on my lap while I petted her after I had released her for several minutes, apparently perfectly content!

I am not an expert, so someone with more experience may have a different comment, BUT..I am looking to integrate three with an existing twosome. I am finding that the size difference is the major issue. At one and one half months, mine are still noticably smaller than my year olds. As long as they are around the same size, they stand a good chance. I have heard they'll need to be visible to the others, but untouchable for a week or so. Then supervised free ranging or time together in their coop. The pecking order needs to be established, but they should be able to handle it as long as they aren't too small.

I just put 2, 6 week olds in with the 17 big hens, a rooster, and the 2 ducks. There was really no fighting, the pullets stay together, and try to mind the space of the others. There is only a little pecking just to show who is higher ranking.

I will be q-tining the new girls in a huge (48" x 30") dog crate, inside a big exercise pen, with the tray removed so it will be like a tractor (can move it around on the grass every day). They will be there during the day and in the house (in a smaller crate) at night.

Once the q-tine period is over I planned to move their dog crate next to the chicken run, and then INTO the chicken run, thereby giving everyone plenty of time to get used to the idea before I turn them loose.

I think it will really help that there will be 2 of them--I originally planned to get 1 but it seemed cruel to subject a single hen to a 30 day q-tine. This way, too, they will have each other and they can just avoid Clarice (big, mean, bossy Alpha Hen) together.

Pawsplus, I don't think you will have much trouble integrating them, since there are as many new ones as old ones. It's hardest to integrate a singleton, or even a few young ones to a large flock.

Kaitie09, I would keep a close watch. Sometimes the big ones will beat up on a new one if they can get her alone. That won't be too hard, since you have only 2 new ones. The older ones can also exclude the new ones from food and water, so be sure your set-up is such that the new ones can access food and water without a fight.

I know. I can see them from my window and check on them periodically. During feeding, I feed outside first, so all the big guys run there, then I lock the pop door and feed inside so the broodies and these 2 pullets can get their fair share. I have seen the older ones chase after the little ones if they get close to them, but they have not actually pecked them. The ducks seems really interested in them too. The female follows them around, but stays about 1ft away from them.